Physiological data can be challenging to obtain, especially when such data relates to the health, operation, and other characteristics of the heart. Cardiac data is commonly obtained through the use of electrocardiograms (ECGs) and/or myocardiograms. Obtaining cardiac data often requires invasive procedures such as catheterization (which involves the acute placement of sensors) and/or the use of imaging techniques such as echocardiography or magnetic resonance imaging (MRI). Acquiring cardiac information via imaging is expensive, time consuming, and resource exhausting.
Implantable medical devices (IMDs) are well known in the medical device field and are known to monitor heart activity, provide pacing therapy, and/or provide defibrillation therapy. In this regard, IMDs can be used to collect physiological data directly from the heart. IMDs commonly employ sensor/electrode leads that obtain electrogram (EGM) readings from heart tissue and/or deliver electrical therapy to the heart tissue as needed. Moreover, IMDs are often designed to support wireless data communication (telemetry) with external devices, e.g., IMD programmers or patient monitors.
EGM or ECG data can be used to evaluate the condition of the heart. At least one known IMD system utilizes an EGM-based electrical marker channel to indicate the occurrence of certain cardiac electrical events such as sensed and paced events associated with the operation of a pacemaker device. The electrical marker channel is derived at least in part from the EGM signal, and the electrical marker channel identifies the occurrence of events such as: ventricular pacing; atrial sensing; atrial refractory sensing; ventricular sensing; and ventricular refractory sensing. Accordingly, electrical marker channels are effective at identifying events that are directly related to sensed electrical activity within the heart. However, electrical marker channels do not convey cardiac information related to chemical or mechanical phenomena.